Good fit, cushioning and shock absorption are challenges facing footwear designers. Inflatable articles have been used in the upper, under the foot, or within the sole of a shoe to enhance a shoe's fit, to provide cushioning and to help absorb shock while standing, walking or running. Inflatable products are particularly desirable for footwear because they are lightweight and can be adjustable to accommodate the particular cushioning, support or fit desired by the wearer.
Some inflatable bladders are inflated at the factory, while others have valves for which to attach inflation mechanisms, such that the individual wearer may adjust the pressure of air, or other fluid, within the inflatable bladder. An on-board inflation mechanism, i.e., an inflation mechanism incorporated directly into or onto a shoe, is particularly convenient and allows the wearer to change the pressure within the inflatable bladder without having to carry around a removable inflation mechanism.
Such on-board inflation mechanisms may be accessible to the wearer from the exterior of the shoe, such that the wearer can manually actuate the inflation mechanism when a pressure increase in the shoe is desired. Alternatively, such an on-board inflation mechanism may be positioned beneath a wearer's foot, so that the downward pressure from the foot with each step automatically actuates the inflation mechanism.
One challenge with on-board inflation mechanisms is providing simplified structures for the pump and valve for inflating the bladder.